Workpiece transfer mechanism

ABSTRACT

The specification discloses a workpiece feeding device for advancing workpieces step by step from an incoming station into a plurality of work stations and then to an outgoing station. The device has frame members reciprocable in the direction of movement of the workpieces and movably carried by the frame members are workpiece engaging elements arranged in opposed relation and movable toward each other to engage workpieces and away from each other to release workpieces. The feeding device is particularly adapted for use with a mechanical press and is arranged to be driven by the press crankshaft so as to operate in timed relation to the movement of the press slide.

United States Patent [151 3,704,775 Eickenhorst 1 Dec. 5, 1972 [54]WORKPIECE TRANSFER MECHANISM [72] Inventor: Frank C. Eickenhorst, Mason,Ohio Primary Examiner Rlcbard Aegener Attorney-Jeffers and Rickert [73]Assignee: The Minster Machine Company,

Minster, Ohio [57] ABSTRACT [22] Filed: Sept. 14, 1970 The specificationdiscloses a workpiece feeding device for advancing workpieces step bystep from an incom- [211 Appl' 71670 ing station into a plurality ofwork stations and then to an outgoing station. The device has framemembers [52] US. Cl ..l98/2l8 reeiproeable in t e direction of movementof the [51] Int. Cl ..B65g 25/04 workpieces and moi/ably ca y the frame[581 Field of Search ..l98/2l8, 19 here are workpiece engaging elementsarranged in pposed relation and movable toward each other to en- [56]References Cited gage workpieces and away from each other to releaseworkpieces. The feeding device is particularly adapted UNITED STATESPATENTS for use with a mechanical press and is arranged to be 3 42driven by the press crankshaft so as to operate in 8,166 v Burke V timedrelation to the movement/of the press Slide 3,262,541 7/1966 DeGam3,430,782 3/1969 Henkel ..198/218 12 Claims, 13 Drawing Figures V Ill?wmll "mul f PATENTEDu'Ec 51922 a 3,704,775

' sum um 11 FIG .s

INvENToR FRANK C. EICKENHORSY HJeHerQRmkerP Attorneys P'ATENTEDnEc 519123704775 sum our 11 I INVENTOQ FRANK CEwxeuuoasr k Jeflers Qlckert-Attorneys PATENTEDnEc 5 m2 saw us or 11 ]NVENTOR FRANK C. EICKENHORST UdeFFe. rs q'QIckev-i- AHorneys PATENTEDnEc 5 I972 SHEET UBUF 11 O QJNvENToR FRANK C. E \CKENHORST' JeFGersQmker-P bdtcrvieys PATENTEDIJEC51972 3,704,775

sum USUF 11 INvENTOR F 8 B FQANK C. EmKEMHoRsT L J wersQmk fl' AttorneysPATENTEDUEE 51972 3.704.775 sum IUUF 11 F56 8C INVENTOR FRANKCElcKEMuoRsT b J eflers Qmkeri' AHornuys WORKPIECE TRANSFER MECHANISMBACKGROUND OF THE INVENTION The present invention relates to a feeddevice for a machine such as a press, in particular a mechanical press,and is especially concerned with a feed device for advancing workpiecesstep by step to a plurality of work stations in succession.

Many workpieces are best formed by passing the workpieces through aseries of work stations in succession arranged in the working area of asingle tool or machine such as a press. Such work stations, or diearrangements, are referred to as progressive dies because the workpieceusually starts as a strip of stock or blank and progressively assumesfinished shape as it passes through the work stations in succession.

In many cases, in connection with press work, a strip of stock is fedfrom a supply thereof and several operations are performed on the strip,usually commencing with blanking and piercing operations and withforming operations following while the workpiece remains attached to theedge portions of the strip. With the workpieces so attached to the edgeportions of the strip, the locating of the workpieces in the successivedie stations is somewhat simplified because the spacing between theworkpieces is always the same and it is only necessary to advance thestrip a predetermined amount following each operation to advance theworkpieces connected thereto the next following work station. 7

However, it is many times not expedient, or possible, to keep aworkpiece attached to an edge portion of the strip and it is evenpreferable in some cases to supply the workpieces to the progressive diein the form of individual blanks which may be at least partially formed.By supplying the workpieces as individual parts, the operations that areto be carried out thereon are completely free of any interference withthe edge portions of a strip of material and more flexibility ispossible in the nature of the work operations that can be carried out.

It is in connection with a feeding device for feeding individualworkpieces in such a progressive die ar- 4 rangement that the presentinvention is particularly concerned.

A primary object of the present invention is the provision of aworkpiece feeding arrangement which will handle individual workpiecesand move the workpieces step by step from an incoming station to aplurality of work stations in succession and then to an outgoingstation, while at all times accurately positioning the workpieces in theseveral stations.

Another object of the present invention is the provision of a feedingdevice of the nature referred to which is so constructed that arelatively small mass is required to be moved during operation of thedeice thereby permitting the device to be operated at high speed.

A still further object of the present invention is the provision of afeeding device of the nature referred to which is so arranged that thework stations along which the device moves the workpieces can readily beexposed without dismantling the entire feeding device.

It is also an object of the present invention to provide a feedingdevice of the nature referred to in which lost motion between relativelymovable parts is kept to a minimum thereby permitting accurate controlof the movements of the various parts of the feeding device.

It is also an object of the present invention to provide a feedingdevice of the nature referred to in which the movements of the variousparts are synchronized and correlated so that workpieces can be engagedand conveyed and released by the device while being accuratelypositioned at all times.

The foregoing objects as well as still other objects and advantages ofthe present invention will become more apparent upon reference to thefollowing detailed specification taken in connection with theaccompanying drawings in which:

FIG. 1 is a view looking in at one side of a press having a feedingdevice according to the present invention;

FIG. 2 is a view looking in at the other side of the press;

FIG. 3A is a view looking in at the press from the front, which is theleft side of FIG. 1, and showing about the left hand half of the pressand feeding device;

FIG. 3B is a view like FIG. 3A, looking in at the front of the press,but showing the right hand half of the press and feeding device;

FIG. 4A is a plan'sectional view indicated by line 4A-4A on FIG. 3A;

FIG. 4B is a plan sectional view indicated by line 4B--4B on FIG. 3B;

FIG. 5 is a fragmentary vertical sectional view indicated by line 5-5 onFIG. 4B;

FIG. 6 is a fragmentary vertical sectional view indicated by line 6-6 onFIG. 3B;

FIG. 7 is a view drawn at enlarged scale and showing an adjustable linkforming a part of one of the drives for the feeding device;

FIG. 8A is a view showing the feeding device from the side at one endthereof and partly in cross section;

FIG. 8B is a view like FIG. 8A but shows the center portion of thefeeding device and is also partly in cross section;

FIG. 8C is a view showing the feeding device from the side at the otherend of the feeding device and is also partly in cross section; and

FIG. 9 is a perspective view showing the general arrangement of thefeeding device as seen from the left front corner.

SUMMARY OF THE INVENTION The feeding device of the present inventioncomprises a main frame adapted for being mounted in the working space ofa press and having frame members guided thereon for reciprocation onopposite sides of, and parallel to, a path along which the incomingstation of the press and the row of work stations and the outgoingstation are arranged.

Each frame member has connected thereto a plurality of workpieceengaging elements arranged along one side of the row of work stations atthe same spacing as the stations and opposed to the correspondingelements on the other frame member. Driving devices are connected to theframe members for causing reciprocation thereof parallel to theaforementioned path and for reciprocating the workpiece engagingelements toward each other to engage workpieces therebetween and awayfrom each other to release workpieces from therebetween.

The frame members reciprocate between end positions spaced apart thesame distance as the stations and carriers which can be swung outwardlyaway from the path along which the work stations are distributed toexpose the work stations when necessary while each frame member togetherwith the adjacent workpiece engaging elements can be swung outwardlyaway from the said path for even greater exposure of the work stations.1

Separate drives are provided for reciprocating the frame membersparallel to the path and for moving the workpiece engaging elementslaterally of the path and a further drive arrangement is arranged ininterconnecting relation thereto to cause the reciprocation of the framemembers and the movement of the workpiece engaging elements to takeplace in fixed timed relation to each other.

The feeding device is especially adapted for use with a mechanical pressand is arranged to receive motive power from the crankshaft ofthe pressfor carrying out one complete workpiece advancing cycle for eachrotation of the press crankshaft.

DETAILED DESCRIPTION Referring to the drawings somewhat more in detail,and particularly to FIGS. 1, 2, 3A, 38, 4A and 4B, the press with whichthe device is used will be seen to comprise bed and a head 12 anduprights 14 extending therebetween. Mounted on bed 10 in the workingspace of the press is a feeding device according to the presentinvention and generally indicated at 16.

The feeding device is adapted for receiving motive power from crankshaft18 mounted in the press head via a slip free flexible drive 19 (FIGS. 1and 3B) which might consist, for example, of the toothed belt 20 runningover the toothed pulley 22 on the crankshaft l8 and a toothed pulley 24on the feeding device and maintained taut by an idler pulley 26 runningon the back of the belt on the slack reach thereof and advantageouslymounted on the'adjacent upright.

Pulley 24 is mounted on a shaft 28 which carries at one end a furtherpulley 30 (FIGS. 1, 3B and 4B). Pulley 30 is also toothed and is engagedby a toothed belt 32 which is entrained about a still further toothedpulley 34 on the input shaft 36 of a drive unit designated at 38 andmounted at one end of the press bed as on a supporting bracket 40 (FIGS.1, 3B and 4B).

As will be seen in FIGS. 1, 3B and 4B, drive unit 38 has an output shaft42 which oscillates in response to rotation of input shaft 36. Connectedto shaft 42 at opposite sides of drive unit 38 are the arms 44 whichwill also oscillate in response to rotation of input shaft 36. An idlerpulley 46 which is carried on the press bed, as on a bracket 48, engagesthe back side of the slack reach of toothed belt 32.

Shaft 28 on which pulleys 24 and 30 are mounted extends in thetransverse, or side to side, direction of the press and preferably has atubular section 49 connected thereto for the purposes of rigidity andlightness. At the side of the press opposite pulleys 24 and 3b, thetubular section 49 is connected to another shaft 50 on which is mounteda toothed pulley 52 (FIGS. 3A and 4A).

As will best be seen in FIG. 2, toothed pulley 52 has another toothedbelt 54 entrained thereabout which also passes about a toothed pulley 56on input shaft 58 of another drive unit 60 mounted on the end of thepress bed, as by supporting bracket 62.

Still another idler pulley 64 is carried by the press bed and engagesthe slack reach of belt 54, in this case, on the inside thereof as amatter of convenience.

Drive unit 60 has an output shaft 66 extending transversely therethroughon the opposite ends of which are mounted the arms 68. Shaft 66 and arms68 will oscillate in response to rotation of input shaft 58.

At this point it will be apparent that power is derived from thecrankshaft of the press and delivered to the feed unit via a first driveconsisting of drive unit 38 and a second drive consisting of drive unit60. A third drive consisting of shafts 28, 49 and 50 and the toothedpulleys and belts pertaining thereto positively interconnects the firstand second drives so that the drives for the feed unit run in timedrelation to each other and in timed relation to rotation of the presscrankshaft.

The feed unit utilizes the press bed 10 and bolster 11 as its mainframe. Framernembers 70 (FIG. 4B) are mounted on the press bed at oneside of the working space of the press, and frame members 72 are mountedon the press bed on the other side of the working space thereof (FIGS.3A, 38, 4A and 4B). The frame members 70 and 72 are located in fixedspaced relation to each other and are keyed to angularly related keyways73 and 74 in the press bed and are clamped in place by the cap screws 76extending through the blocks and into the press bed. The keyways 73 and74 and the keys therein will be seen in FIGS. 8A and 8C.

The main frame of the unit also comprises a bolster arrangement 11secured to the press bed 10 and comprising upwardly facing rail regions78 (FIGS. 4A and 4B) extending in parallel spaced relation in the sideto side direction across the bed and on opposite sides of a die spacegenerally designated at 80. The rail regions 78 may be integral with abolster member or may be formed on separate parts which are preferablyinterconnected by frame members therebeneath which are, in turn, boltedto the press bed or bolster.

As will be seen in FIGS. 4A and 4B, in the space 80, and arranged in aline, or along a path, parallel to rail regions 78 are the dies formingthe work stations 82 in predetermined longitudinally spaced relation. Atone end of the row of work stations is an incoming station 34 to whichworkpieces in the form, for example, of blanks to be processed aresupplied by an incoming conveyor such as belt 86 while at the oppositeend of the row of work stations is an outgoing station 88 which maycommunicate with a workpiece receiver via a chute or the like.

Incoming station 84 and outgoing station 88 are spaced from the nextadjacent work stations the same distance that the work stations arespaced from each other.

Extending between frame members 70 and 72 on each side of the pathrepresented by space are guide means in the form of superimposed shafts90 and 92 which are parallel with each other and also parallel with theaforementioned space 80 (FIGS. 4A, 48, 8A and 8B). Both of the shaftsare rotatably carried in the frame members 70 and 72 by antifrictionbearings 91 and 93 (FIG. 8C) and each pair of shafts together form aguide way for frame members 96, 98 and 100 (FIG. 88) on the respectiveside of the path. Each frame member is reciprocable longitudinally alongthe respective pair of shafts.

As will be seen in FIGS. 8A and 8B, the bearing supporting portions 96,98 and 100 are connected by tubular portions 97 so that each framemember, while light in weight, is strong and rigid. The bearingscontained in said bearing portions for the shafts are preferably in theform of ball nuts 95 having infinite pitch and the shafts 90 and 92 are,therefore, provided with external splines for nonrotatively engaging therespective ball nuts 95.

According to the present invention, at least the ball nuts 95 in theends of each frame member pertaining to the upper shaft 90 extendingthrough the respective frame member are adapted for being adjustedrelatively angularly about the axis of the said shaft and clamped inadjusted positions thereby to hold the said upper shaft in torsion andthereby to eliminate lost motion between the shaft and the ball nuts.

This arrangement is resorted'to because each of the ball nuts pertainingto the upper shaft of each frame member has connected thereto andextending upwardly through the top of the frame member an actuatinglever 102. Each actuating lever 102 is rotatably supported in therespective frame member by antifriction bearings 103 and at its upperend has connected thereto a laterally extending cross head 104 whichpivotally receives the bifurcated rear end of a link 106. Each link 106extends toward space 80 and at its end adjacent space 80 is connected byspherical pivot joints 108 with a bar-like carrier member 110 slidablyresting on top of the adjacent rail region 78.

Each carrier member 110 is retained in sliding engagement with its railregion 78 by clamp elements 112 pivoted at 114 to respective blocks 116mounted at the sides of the rail region 78. Screws 118 extending throughthe clamp elements into blocks 116 hold the clamp elements down againstthe carrier members. The carrier members 110 may be provided withhardened wear plates on top thereof, if desired.

It will be evident, however, that releasing of screws 118 will permitthe carrier members 110 and links 196 to be swung upwardly about thepivotal connections of the links with the upper ends of levers 102 so asto expose the adjacent side of space 80.

Connected to carrier members 110 and extending therefrom toward thecenter of space 80 are the workpiece engaging elements 120 contoured onthe inner ends to engage workpieces in the respective stations.

.The workpiece engaging elements on each carrier member are spaced thesame distance as the stations distributed along space 80 and are inopposed relation to those carried by the other carrier member.

At this point it will be appreciated that rocking of the upper shafts 90in the frame members 96, 98 and 100 will cause rocking of the levers 102connected therewith and, through links 106, effect movement of thecarriers 110 and the workpiece engaging elements 120 mounted thereontransversely of the center line of space 80. Also, it will be evidentthat longitudinal movement of the aforementioned frame members 96, 98and 190 in a direction parallel to space 80 will cause movement in thesame direction of the carrier members and the work engaging elementsmounted thereon.

Rocking of shafts 90 is accomplished by the arms mounted on the shafts132 which are detachably connected by coupling blocks 134 to the shafts90.

Each arm 130 is connected with a respective one of arms 68 by a linkmade in the form of a turnbuckle, as shown in FIG. 7, so as to beadjustable in length. Due to the adjustable length of links 140, arms 68can oscillate between predetermined fixed limits and the precise limitsof oscillation of workpiece engaging elements 120 can be adjustedrelative to the center line of space As to the reciprocation of framemembers 96, 98 and 100 at the ends thereof adjacent drive unit 38, eachframe member has connected thereto a rod extending axially therefrom andslidably guided in the adjacent main frame member 70. Preferably, theframe member end of each rod 150 is clamped to the respective framemember with an adjustable spacer member 152 interposed between the framemember and the pertaining rod.

Each rod 150 is connected by coupling 154 with a link 156 extending tothe outer end of a respective arm 44 pertaining to drive unit 38 andpivotally connected thereto. It will be appreciated that oscillation ofarms 44 will effect reciprocating movement of the frame members whilethe precise end positions of the frame members can be adjusted by theselection of the thickness of spacer members or washers 152.

The bearings 91 and 93 at the opposite ends of upper shafts 90 arecarried in blocks 160 which form a part of the aforementioned framemembers 70 and 72. The portion of each of the frame members 70 and 72 onwhich blocks 160 rest is formed with an arcuate guide way 162 concentricwith the axis of the respective lower shaft 92 and each block 160 isslidable on a respective guide way 162. Means are provided in the formof a pull out dowel pin, for example, as indicated at 164, forreleasably locating each block in the position wherein the shaft 90pertaining thereto is in its upper operative position as illustrated inthe drawings. Screws clamp each block 160 in the upper position thereofon the respective frame members 70, 72.

However, by removing screws 165 and by pulling dowels 164;, anduncoupling rods 150 from the frame members, and uncoupling shafts 90from shafts 132 by opening the couplings 134, and releasing clampelements 112, each frame member together with the carrier member 110connected thereto and the workpiece engaging elements 120 can be swungoutwardly away from space 80 thereby to expose the space forinstallation, removal, repair, or adjustment of dies mounted therein.

It will be appreciated that the individual work engaging elements can bevaried as to the precise size and configuration thereof to take intoaccount changes in contour of the workpiece as it advances through theseveral work stations.

In operation, the said device is timed relative to the press so that, asthe press slide moves upwardly, the carrier members and the workengaging elements of the feed device move in unison toward each otherand grip therebetween the workpieces extending along the center line ofthe path along which the work stations are arranged. During continuedupward movement of the press slide, the carrier members and framemembers of the feed device are advanced laterally in the press adistance equal to the space between adjacent stations.

At about the time the press slide begins its downward stroke, theworkpieces are accurately located in advanced'position and the carriermembers and work en'- gaging elements retract outwardly and release theworkpieces. The frame members and carrier members then move backwardlyto the original position thereof during further downward movement of thepress slide, preparatory to a new cycle of operations.

Modifications may be made within the purview of the appended claims.

What is claimed is:

1. In a transfer mechanism for moving workpieces step by step from anincoming station into a plurality of work stations in sequence and thento an outgoing station, said stations being spaced uniformly along apath; said mechanism comprising a main frame defining the said-path, aframe member on each side of said path, guide means including two pairsof parallel guideways carried by the main frame guiding said framemembers for reciprocation parallel to said path, said guideways having apair of shafts provided with angularly adjustment means to place suchshafts in torsion to eliminate lost motion in said shafts, first meansconnected to said frame members for reciprocation thereof in unisonbetween first and second end positions spaced substantially the samedistance as adjacent stations, workpiece engaging elements carried bysaid frame members to reciprocate therewith and movable thereonlaterally of said path, the said elements on said frame members beingdistributed therealong in opposed relation at the same spacing as saidstations, second means for moving said elements in unison on said framemembers laterally toward and away from said path alternately to gripworkpieces in said station and to release workpieces to said stations,and third means operativelyinterconnecting said first and second meansfor operation thereof in timed relation to advance workpieces step bystep from said incoming station to said work stations in sequence andfinally to said outgoing station.

2. A transfer mechanism according to claim 1, in which said guide meanscomprises two pairs of shaft means carried by said main frame parallelto said path on each side thereof and slidably supporting said framemembers.

3. A transfer mechanism according to claim 1, in which said guide meansfor each frame member comprises a pair of parallel shafts supported insaid main frame in vertically upper and lower spaced relation, eachframe member comprising a hollow box-like structure having bearing meanstherein slidably engaging the respective shafts.

4. A transfer mechanism according to claim 3, in which the upper one ofthe shafts for each frame member is connected to said second drive to beactuated thereby, a plurality of levers in longitudinally spacedrelation in each frame member and rotatable thereon, said levers beingnonrotatively connected to the respective upper shaft, a carrier memberparallel to said path on each side thereof and having the adjacent saidworkpiece engaging elements connected thereto,

said main frame including means for guiding said carrier members thereonfor movement laterally of said path and parallel to said path, and linksconnecting the said levers of each frame with the adjacent said carriermember.

5. A transfer mechanism according to claim 4, in which said means forguiding said carrier members comprises upwardly facing surfaces on saidmain frame on each side of said path on which said carrier membersslidably rest and clamp elements movably connected to said main frameand overlying said carrier elements, said links of each said framemember being pivotal on the respective said levers about a common axisparallel to said path whereby releasing of said clamp elements willpermit said carrier members and the said elements carried thereby to bepivoted upwardly and outwardly away from said path.

6. A transfer mechanism according to claim 5, in which .said main frameincludes a support block supporting each end of the upper one of theshafts for each frame member, means guiding each block for movementabout the axis of the adjacent lower one of said shafts away from saidpath and downwardly, and releasable means detachably retaining eachblock on said main frame within the position wherein the respectiveupper shaft is in operative position, said clamp elements and releasablemeans being releasable for bodily pivoting of each said frame member andthe respective carrier members and the work engaging elements thereonabout the axis of the respective lower shaft.

7. A transfer mechanism according to claim 6, in which said first meansis detachable from said frame members and said second means isdetachable from said upper shafts for completely freeing said framemembers for pivoting movement about the respective lower shafts toexpose the region along said path adjacent to said stations.

8. A transfer mechanism according to claim 4, in which said second driveincludes oscillatory output shaft means and drive arms thereon, otherarms connected to the said upper shafts, and links interconnecting eachdrive arm with a respective said other arm and adjustable in length topermit precise adjustment of the limits of lateral movement of saidcarrier members and the said workpiece engaging elements carriedthereby.

9. A transfer mechanism according to claim 4, in which at least saidupper shafts are splined and said bearings are in the form ofcirculating ball nuts with infinite pitch, one of said nuts beingdisposed near each end of the respective frame member and beingrotatable in the frame member and supporting a respective one of thesaid levers. I

10. A transfer mechanism according to claim 9., in which eachframemember includes at least one further ball nut rotatable therein andnonrotatively engaging the respective said upper shaft and supporting afurther one of said levers.

11. A transfer mechanism according to claim 3, wherein bearings areprovided for at least the upper one of each pair of shafts in the formof ball nuts near the ends of the respective frame members forming atorsion coupling with the respective shaft, and means for adjusting saidnuts circumferentially to place the respective shaft in torsion.

3,704,775 9 10 12. A transfer mechanism according to claim 11, whichincludes ball joints on at least one end of said links connecting thelinks with said carrier members.

- UNITED STATES PATENT OFFICE CERTIFICATE CORRECTION Patent No.3,704,775 I Dated D cember 5, 1972 InventOr(s) Frank C. Eickenhorst Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Col. 1, line 30', "to" omitted between "thereto" and "the" Col. 1, line56, "deice" should be device 7 Col. 8 line 4, (Claim 4) "member" omittedbetween "frame" and "with".

Signedand sealed this 1st day of May 1973.

(SEAL Attes I ED11511 l-l. JR. ROBERT GOTTSCHALK Attesting OfficerCommissioner of Patents

1. In a transfer mechanism for moving workpieces step by step from anincoming station into a plurality of work stations in sequence and thento an outgoing station, said stations being spaced uniformly along apath; said mechanism comprising a main frame defining the said path, aframe member on each side of said path, guide means including two pairsof parallel guideways carried by the main frame guiding said framemembers for reciprocation parallel to said path, said guideways having apair of shafts provided with angularly adjustment means to place suchshafts in torsion to eliminate lost motion in said shafts, first meansconnected to said frame members for reciprocation thereof in unisonbetween first and second end positions spaced substantially the samedistance as adjacent stations, workpiece engaging elements carried bysaid frame members to reciprocate therewith and movable thereonlaterally of said path, the said elements on said frame members beingdistributed therealong in opposed relation at the same spacing as saidstations, second means for moving said elements in unison on said framemembers laterally toward and away from said path alternately to gripworkpieces in said station and to release workpieces to said stations,and third means operatively interconnecting said first and second meansfor operation thereof in timed relation to advance workpieces step bystep from said incoming station to said work stations in sequence andfinally to said outgoing station.
 2. A transfer mechanism according toclaim 1, in which said guide means comprises two pairs of shaft meanscarried by said main frame parallel to said path on each side thereofand slidably supporting said frame members.
 3. A transfer mechanismaccording to claim 1, in which said guide means for each frame membercomprises a pair of parallel shafts supported in said main frame invertically upper and lower spaced relation, each frame member comprisinga hollow box-like structure having bearing means therein slidablyengaging the respective shafts.
 4. A transfer mechanism according toclaim 3, in which the upper one of the shafts for each frame member isconnected to said second drive to be actuated thereby, a plurality oflevers in longitudinally spaced relation in each frame member androtatable thereon, said levers being nonrotatively connected to therespective upper shaft, a carrier member parallel to said path on eachside thereof and having the adjacent said workpiece engaging elementsconnected thereto, said main frame including means for guiding saidcarrier members thereon for movement laterally of saiD path and parallelto said path, and links connecting the said levers of each frame withthe adjacent said carrier member.
 5. A transfer mechanism according toclaim 4, in which said means for guiding said carrier members comprisesupwardly facing surfaces on said main frame on each side of said path onwhich said carrier members slidably rest and clamp elements movablyconnected to said main frame and overlying said carrier elements, saidlinks of each said frame member being pivotal on the respective saidlevers about a common axis parallel to said path whereby releasing ofsaid clamp elements will permit said carrier members and the saidelements carried thereby to be pivoted upwardly and outwardly away fromsaid path.
 6. A transfer mechanism according to claim 5, in which saidmain frame includes a support block supporting each end of the upper oneof the shafts for each frame member, means guiding each block formovement about the axis of the adjacent lower one of said shafts awayfrom said path and downwardly, and releasable means detachably retainingeach block on said main frame within the position wherein the respectiveupper shaft is in operative position, said clamp elements and releasablemeans being releasable for bodily pivoting of each said frame member andthe respective carrier members and the work engaging elements thereonabout the axis of the respective lower shaft.
 7. A transfer mechanismaccording to claim 6, in which said first means is detachable from saidframe members and said second means is detachable from said upper shaftsfor completely freeing said frame members for pivoting movement aboutthe respective lower shafts to expose the region along said pathadjacent to said stations.
 8. A transfer mechanism according to claim 4,in which said second drive includes oscillatory output shaft means anddrive arms thereon, other arms connected to the said upper shafts, andlinks interconnecting each drive arm with a respective said other armand adjustable in length to permit precise adjustment of the limits oflateral movement of said carrier members and the said workpiece engagingelements carried thereby.
 9. A transfer mechanism according to claim 4,in which at least said upper shafts are splined and said bearings are inthe form of circulating ball nuts with infinite pitch, one of said nutsbeing disposed near each end of the respective frame member and beingrotatable in the frame member and supporting a respective one of thesaid levers.
 10. A transfer mechanism according to claim 9, in whicheach frame member includes at least one further ball nut rotatabletherein and nonrotatively engaging the respective said upper shaft andsupporting a further one of said levers.
 11. A transfer mechanismaccording to claim 3, wherein bearings are provided for at least theupper one of each pair of shafts in the form of ball nuts near the endsof the respective frame members forming a torsion coupling with therespective shaft, and means for adjusting said nuts circumferentially toplace the respective shaft in torsion.
 12. A transfer mechanismaccording to claim 11, which includes ball joints on at least one end ofsaid links connecting the links with said carrier members.